U.S. patent number 5,755,743 [Application Number 08/733,140] was granted by the patent office on 1998-05-26 for implantable unit.
This patent grant is currently assigned to IMPLEX GmbH Spezialhorgerate. Invention is credited to Hans Leysieffer, Andreas Volz.
United States Patent |
5,755,743 |
Volz , et al. |
May 26, 1998 |
Implantable unit
Abstract
An implantable unit with at least one contact arrangement for
connection of an electrical or electronic device (11), which is
hermetically sealed within a housing (10), to at least one cable
set (12, 14) that is routed out of the housing. The contact
arrangement has a first contact (22), a second contact (30)
supported on an elastic body (16), a closing mechanism (18, 19, 20)
for engaging the front of the first contact to the front of the
second contact and at least one sealing land (28) which surrounds
the first contact, which is pressed into the elastic body when the
contacts engage, and which seals the contacts relative to the
outside of the unit.
Inventors: |
Volz; Andreas (Munchen,
DE), Leysieffer; Hans (Taufkirchen, DE) |
Assignee: |
IMPLEX GmbH Spezialhorgerate
(Ismaning, DE)
|
Family
ID: |
7796276 |
Appl.
No.: |
08/733,140 |
Filed: |
October 16, 1996 |
Foreign Application Priority Data
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Jun 5, 1996 [DE] |
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196 22 669.4 |
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Current U.S.
Class: |
607/37;
607/36 |
Current CPC
Class: |
A61N
1/3754 (20130101); H01R 13/5219 (20130101); H01R
13/24 (20130101); H01R 2201/12 (20130101) |
Current International
Class: |
A61N
1/372 (20060101); A61N 1/375 (20060101); H01R
13/52 (20060101); H01R 13/24 (20060101); H01R
13/22 (20060101); A61N 001/375 () |
Field of
Search: |
;607/36,37 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 006 281 |
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Jul 1978 |
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EP |
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0 001 897 |
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May 1979 |
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EP |
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0 052 879 A1 |
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Jun 1982 |
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EP |
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0 052 690 A1 |
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Jun 1982 |
|
EP |
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0 052 879 B1 |
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Sep 1985 |
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EP |
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0 306 443 |
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Mar 1989 |
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EP |
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0 339 877 |
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Nov 1989 |
|
EP |
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0 357 941 |
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Mar 1990 |
|
EP |
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0 442 807 A1 |
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Aug 1991 |
|
EP |
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0 587 379 A2 |
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Mar 1994 |
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EP |
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34 00 191 A1 |
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Aug 1984 |
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DE |
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33 31 620 A1 |
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Mar 1994 |
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DE |
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WO89/05170 |
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Jun 1989 |
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WO |
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WO90/02581 |
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Mar 1990 |
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WO |
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WO91/04069 |
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Apr 1991 |
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WO |
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WO91/16947 |
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Nov 1991 |
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WO |
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WO93/02742 |
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Feb 1993 |
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WO |
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WO93/05844 |
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Apr 1993 |
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WO |
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Primary Examiner: Getzow; Scott M.
Attorney, Agent or Firm: Sixbey, Friedman, Leedom &
Ferguson Safran; David S.
Claims
We claim:
1. Implantable unit comprising a housing, at least one cable set
and at least one contact arrangement for electrical connection of
an electrical or electronic device which is hermetically sealed
within the housing to said at least one cable set routed out of the
housing; wherein the contact arrangement has a first contact,
second contact supported on an elastic body, and a closing
mechanism for engaging a front of the first contact with a front of
the second contact and at least one sealing bridge which surrounds
the first contact, and which is pressed into the elastic body when
the contacts are engaged, said at least one sealing bridge sealing
the contacts relative to the exterior of the unit.
2. Implantable unit according to claim 1, wherein said at least one
sealing land comprises a plurality of concentric sealing lands.
3. Implantable unit according to claim 1, wherein said at least one
contact arrangement comprises a plurality of contact arrangements;
and wherein at least one sealing land is provided for each contact
arrangement.
4. Implantable unit according to claim 1, wherein the first contact
is fixed to the housing and is joined to the electrical or
electronic device; and wherein the second contact is connected to
the cable set.
5. Implantable unit according to claim 4, wherein the first contact
is formed directly by a housing feedthrough of the electrical or
electronic device; and wherein an electrically insulating molding
surrounds the housing feedthrough.
6. Implantable unit according to claim 1, wherein the second
contact is mounted to the housing and is connected to the
electrical or electronic device in the housing; and wherein the
first contact is connected to the at least one cable set.
7. Implantable unit according to claim 1, wherein the closing
mechanism comprises a sealing cap which is connected to the at
least one cable set and in which at least one of said first and
second contacts is located, and an engagement arrangement for
connecting the sealing cap to the housing.
8. Implantable unit according to claim 7, wherein the engagement
arrangement has at least one threaded receptacle on the housing and
at least one screw on the sealing cap.
9. Implantable unit according to claim 7, wherein the engagement
arrangement has a catch connection which acts between the sealing
cap and the housing.
10. Implantable unit according to claim 1, wherein a terminal
fitting is provided on said at least one cable set and which
terminal fitting carries at least one of said first and second
contacts; wherein the closing mechanism has a sealing cap with a
receiver for the at least one terminal fitting; and wherein an
engagement arrangement is provided for connecting the sealing cap
to the housing.
11. Implantable unit according to claim 10, wherein the engagement
arrangement has at least one threaded receptacle on the housing and
at least one screw on the sealing cap.
12. Implantable unit according to claim 10, wherein the engagement
arrangement has a catch connection which acts between the sealing
cap and the housing.
13. Implantable unit according to claim 1, wherein a terminal
fitting is provided on said at least one cable set; wherein the
housing has a trough-shaped receiver holding at least one terminal
fitting at an end thereof; and wherein a wedge member is inserted
between a side wall of the trough-shaped receiver which faces said
end of the housing and the terminal fitting.
14. Implantable unit according to 13, wherein at least one screw is
provided for adjusting and fixing the position of said wedge and
for adjusting the force of the engagement between the first and
second contacts.
15. Implantable unit according to claim 1, wherein the elastic body
is made of silicone.
16. Implantable unit according to claim 1, wherein one of the first
and second contacts has a rounded engagement surface.
17. Implantable unit according to claim 16, wherein the other of
said first and second contacts has a generally flat surface which
is engaged by said rounded engagement surface.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an implantable unit with at least one
contact arrangement for connection of an electrical or electronic
device, which is hermetically sealed in a housing, to at least one
cable set routed out of the housing. In particular, the invention
relates to a detachable electrical connection between an implant
housing which accommodates active electronic components and sensors
or actuators which can be placed at an entirely defined location in
the body and which are operated by the active electronic
components.
2. Description of Related Art
Implantable plug-and-socket connections are used in cardiac
pacemakers, defibrillators and cardioverters. When the implanted
electronics are replaced, which becomes necessary due to the power
source being drained, the sensors and actuators, which require
complex surgical techniques when being implanted or explanted, are
left on site, if possible. In cardiac pacemakers, this has led to a
standard, so that different models can be connected to the sensors
and actuators once they are in place. The requirements for the
electrode plug and the socket are set forth in DIN VDE 0750 Part 91
which also contains an exact stipulation of the dimensions and
tolerances. Plugs designed according to this DIN standard work like
a banana plug, but have two contact surfaces with different
diameters which are separated from one another by sealing O-rings
(sealing lips). The dimensions of the plug receiver are likewise
established according to the plug in this DIN standard. The
diameters of the sealing lips and the plug receiver determine the
contact pressure and the sealing action against penetrating bodily
fluid which can be achieved with it. The standard furthermore
contains test specifications relating to the insulation impedance
which must be greater than 50 k.OMEGA..
Numerous patents relate to production engineering of the plug
receiver on a hermetically sealed housing, the production
engineering of the plug, the type of contact making, and fixing of
the plug in the plug housing. All the following patents have in
common a cylindrical opening for holding a cylindrical plug with
one or more contact points and insulating sealing lips:
European Applications 0 052 690; EP-A-0 006 281; EP-B-0 052 879;
EP-A-0 442 807 and EP-A-0 357 941; U.S. Pat. No. 4,262,673; and
International Applications WO-A-90/02581; WO-A-91/04069;
WO-A-91/16947; WO-A-93/05844; WO-A-93/02742; and WO-A-89/05170.
European Applications EP-A-0 587 379 and EP-A-0 306 443 relate to a
coaxial embodiment of the described plug-and-socket connection
system.
European Application EP-A-0 339 877 calls for making contact with
the cylindrical plug using conductive silicone in the plug
receiver. By alternating conductive and nonconductive layers,
several contacts can be made on the cylindrical plug. Since both
the contacts as well as the insulators are flexible, the formation
of sealing lips can be abandoned by corresponding contact pressure,
both in the contact zone and also in the insulating zone, by
matching the diameters of the plug receiver and of the pin. The
contact pressure is limited by the slide path which must be
traversed when the plug is inserted.
German Patent Application DE-A-33 31 620 differs from the
cylindrical plug which can contain several contact surfaces which
are insulated from one another by sealing lips, and calls for
several contact pins which project vertically from a plug base
plate. O-rings placed around the contacts provide for the seal when
the plug base plate is screwed against the housing. By using screws
to produce the sealing action, a much higher contact pressure can
be achieved, since this pressure need not be overcome when the
plug, is manually inserted. The inventor specifies a gas-tight
seal. This document represents the closest prior art for the
invention described below which, likewise, imposes higher demands
on the insulation between the contacts.
European Application EP-A-0 001 897 describes the possibility of an
electrical connection between two substrates using alternating
layers of nonconductive and conductive silicones. It is assumed
that the substrates are located directly in the bodily medium.
Implants of the initially mentioned type, for example, implantable
hearing aids, cardiac pacemakers, drug pumps, etc. should take up
as little space as possible upon implantation in the body and thus
they should be largely miniaturized. If in the course of this
miniaturization the plug-and-socket connections known from the
prior art are likewise miniaturized, plug,-and-socket connections
are obtained with very thin, elongated contacts which can be easily
broken off, bent or otherwise damaged when inserted into the
corresponding socket.
SUMMARY OF THE INVENTION
Therefore, a primary object of the present invention is to devise
an implantable unit of the initially mentioned type, in which, on
the one hand, a high degree of miniaturization can be achieved
without using overly sensitive components, and in which, on the
other hand, provisions are made for safe and reliable contact
between the device accommodated in the housing and the cable
set(s).
This object is achieved according to preferred embodiments of the
invention by the fact that, in an implantable unit of the initially
mentioned type, the contact arrangement has a first contact, a
second contact supported on an elastic body, a closing mechanism
for engaging the front of the first contact to the front of the
second contact, and at least one sealing land which surrounds the
first contact, which is pressed into the elastic body when the
contacts engage, and seals the contacts relative to the
outside.
In this way, an electronic contact principle is obtained which has
no socket and no plug to be inserted into the socket. By using two
contact elements which are pressed against one another on the front
and which can be made more or less flat, a high degree of
miniaturization is possible, since the danger of breaking or
bending of thin plug pins can be precluded and the necessary depth
for the plug path is eliminated. Both the contact force as well as
the force which is necessary to seal the contacts against
penetrating bodily fluid are produced via the same closing
mechanism. By choosing a correspondingly high pressure, on the one
hand, a reliable, gas-tight connection which is functionally
equivalent to a weld connection is formed at the point of contact
between the contacts. On the other hand, the contacts are
hermetically sealed, for example, against the penetration of body
fluid.
In order to further improve the sealing action, a plurality of
sealing lands which are concentric to one another can be provided,
for which, when using a plurality of contact arrangements, for each
contact arrangement, there can be at least one sealing land which
is assigned to this contact arrangement.
If the first contact is fixed to the housing and is joined to the
electrical or electronic device which is accommodated in the
housing, while the second contact is connected to the cable set,
the first contact can be formed directly by a feedthrough of the
electrical or electronic device through the housing; in this case,
preferably, an electrically insulating molding is provided which
surrounds the feedthrough.
According to one embodiment of the invention, the closing mechanism
has a sealing cap which is connected to at least one cable set, and
in which there is at least a first contact and/or at least a second
contact, the engagement arrangement being provided in order to keep
the sealing cap engaged to the housing. In this case, the sealing
cap with the contacts located therein forms a unit which can be
attached, for example, via a thread assigned to the housing and a
screw assigned to the sealing cap on the housing. Alternatively,
there can be a catch connection which acts between the sealing cap
and the housing.
If replacement of only the cable set is to be possible, it is
advantageous if the cable set is provided with a terminal fitting
which bears one or more first or second contacts, and if the
closing mechanism has a sealing cap with a receiver for the
terminal fitting. The possibility of replacing the cable set is
especially advantageous when several cable sets are to be connected
to the device accommodated in the housing. In this embodiment, a
screw and a threaded receptacle for it, or a catch connection, are
also used to keep the sealing cap engaged to the housing.
If a screw is used for engagement between the sealing cap and the
housing, the arrangement is such that, for contacting between the
first and the second contacts, a specific torque which is applied
to the screw is necessary. By using a suitable tool, especially a
torque wrench, excess stress is avoided, both of the screw and also
of the components which come into contact with one another, yet,
the surgeon can still be certain that the desired contacts are
established. Furthermore, the closing force can thus be reliably
introduced even with a large number of seals and contacts to be
closed.
Depending on the type of device to be implanted, it can be
advantageous if the terminal fittings are inserted in a direction
perpendicular to the cable sets, and if the force for connecting
the contacts can be applied in a direction perpendicularly to the
direction of the action of this force. For this reason, in another
embodiment of the invention, on at least one cable set, there can
be a terminal fitting and the housing can have a trough-shaped
elongation to hold at least one terminal fitting. Furthermore,
there can be a wedge for insertion between the wall side of the
trough-shaped elongation, which is at a distance from the housing,
and a terminal fitting which is inserted into the trough-shaped
elongation. If the wedge is, for example, inserted and fixed by
means of a screw provided especially for this purpose, it presses
the terminal fitting in the direction perpendicular to the screw
axis against the housing.
By this path-force transformation, the closing mechanism can be
operated from above also for a housing which is implanted parallel
to the surface of the patient's skin, as, for example, a housing
embedded in the skull bone, so that, to replace or couple the cable
set, the housing need not be removed from its fixed anchor, as, for
example, a bone bed. Thus, the treating surgeon has both hands free
for the connection process and he need not hold the housing for the
connection process, as in conventional arrangements. The danger of
applying tension during connection to the lines which are joined to
the actuators or sensors, which can lead to damage of the lines,
which are very thin if necessary (especially for multichannel
systems), or of sensors and actuators, is thus largely prevented.
In many conventional devices in which first the connection process
must be completed before they are placed at the final implantation
site, moreover, for the connection process, a certain length of
excess cable is necessary which is placed at the implantation site
in a loop around the housing. In contrast, the coupling principle
proposed here enables direct and short line paths between the
device accommodated in the housing and the sensor or actuator
components which are connected thereto.
To fix the wedge in position, however, between it and the housing
there can be a catch device, so that the wedge can be manually
inserted and a tool for operating the screw can be dispensed
with.
Preferred embodiments of the invention are detailed in the
following with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a sectional view of an implantable housing;
FIG. 2 shows a schematic perspective view of a portion of the front
side of the housing shown in FIG. 1;
FIG. 3 is a sectional view showing part of an implantable housing
similar to FIG. 1;
FIG. 4 shows a view similar to FIG. 3 of a modified version of the
housing shown in FIG. 1;
FIG. 5 shows an enlarged sectional view of a contact arrangement in
the closed state;
FIG. 6 shows a sectional view of the FIG. 5 contact arrangement in
the opened state;
FIG. 7 is a perspective view of an implantable housing according to
another embodiment; and
FIG. 8 is an exploded perspective view of the implantable housing
shown in FIG. 7 and the components used for fixing the contacts and
for sealing the housing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a section through an implantable unit having a
hermetically sealed housing 10 for holding an electrical or
electronic device 11, shown as a block, which can be, for example,
the signal converter of an implantable hearing aid, the signal
processing electronics of a cardiac pacemaker, etc. The connection
of the device accommodated in hermetically sealed housing 10 with
actuator or sensor components 13, 15, shown likewise only as
blocks, is effected via cable sets 12, 14. The ends of cable sets
12, 14 are embedded in terminal fittings 16 which are inserted in
an end cap 18 that is provided on the front of housing 10 when the
unit is implanted. A screw connection is formed by a screw 20 which
is carried by the sealing cap 18 and a threaded receptacle 19
carried by the housing 10 and is used to fix terminal fittings 16.
FIG. 1 shows an embodiment for an implantable unit with a sensor
and an actuator element 13, 15 which can be arranged separately
from one another in space, and which, therefore, require their own
cable set. However, it goes without saying that the principle
described below can be implemented in the same way in embodiments
with only one cable set or with more than two cable sets. If the
sensor and actuator channels lead to different implantation sites,
there should be one cable set per implantation site, the terminal
fitting of which can be removed independently from the others, so
that a fault in the sensors or actuators does not necessitate a
complete new operation (RE-OP).
To form the housing-side contacts, on the front of housing 10,
there are feedthroughs 22 with flat front side, which are separated
by insulator 24, for example, ceramic, from the housing generally
made of metal body, and which are held rigidly. Insulator 24,
furthermore, provides a hermetic seal between the feedthroughs 22
and the housing 10. On the side of housing 10 which contains the
wire-shaped feedthroughs 22, a molding 26 of electrically insulated
inelastic material, for example, of a polycarbonate, is attached,
with the front end surfaces of the feedthrough wires 22 lying flush
with the front surface of the molding 26. To seal the contact
surfaces of the front end surfaces of the feedthrough wires 22
against contact with body fluids, the molding 26 has one or more
sealing lands 28 which project forwardly from its front surface.
These sealing lands 28 are buried in the terminal fittings 16
(which are made of an elastic material) when the housing 10 and end
cap 18 are screwed together.
In the embodiment shown in FIG. 1, as is especially apparent from
FIG. 2, two circular sealing lands 28 concentrically surround each
of the feedthroughs 22. Instead or in addition, sealing lands can
also be provided which surround several contacts, for example, the
contacts assigned to one terminal fitting or even all contacts of
the entire unit.
The dimensions of the molding 26, the terminal fittings 16 and end
cap 18 are selected such that the elastic material of terminal
fittings 16, which is preferably silicone, is not stressed beyond
its elastic limit when end cap 18 is screwed on, so that a
resilient restoration force is preserved which produces a high
pressure on the sealing lands and which is designated sealing force
F.sub.D in FIG. 5. In this same way, when end cap 18 is screwed on,
a spring-like contact force F.sub.K is produced between
feedthroughs 22 and the cap-side contacts 30 which are embedded in
the elastic material of the terminal fittings 16, by pushing
contacts 30, when they meet the nonreceding contact surfaces of
feedthroughs 22, into the elastic material of terminal fittings 16.
Contact force F.sub.K is preferably selected to be so large that
the surfaces of the metal contacts begin to flow and ensure a
gas-tight seal of the point of contact.
Preferably, in the manner shown for contacts 30, one of two
mutually engaging contacts has a rounded front side in order to
obviate the necessity to maintain unnecessarily high precision with
regard to parallelism for multiple planar contacts. The required
contact force depends on the metallic material and the required
contact surface (current carrying capacity). The elastic limit of
the elastic material for a given bearing surface of the contact,
which must be much greater than the actual contact surface, is a
limiting factor.
The spatial arrangement of the rigid molding provided with sealing
lands and of the elastic body can be interchanged, if desired, as
shown in FIG. 3 where, in this case, an elastic body 32 is applied
to the front side of housing 10, for example, by means of cementing
or glueing, and a rigid terminal fitting 34 analogous to molding 26
in FIGS. 1 and 2 is applied to end cap 18. The two contacts 30 are
embedded in elastic body 32 and are provided with a front surface
which is approximately hemispherically rounded. Contacts 30 are
joined via connection wires 33 (which are electrically sealed
relative to housing 10 by means of insulators 24) to the electrical
or electronic device which is accommodated within the housing 10.
According to this embodiment, the end of cable set 14 is connected
to two disk-shaped contacts 36 that have a flat front surface and
are embedded in the rigid terminal fitting 34 within the
ring-shaped sealing lands.
In order to prevent confusion of the cable sets during implantation
of the unit, the terminal fittings are preferably coded or differ
in shape and/or size. Another possibility consists in providing one
of the two cable sets, for example, the cable which leads to an
actuator, with a terminal fitting according to FIG. 1, while for
the other cable set, for example, the cable which leads to a
sensor, there is a terminal fitting according to FIG. 3. It goes
without saying that the front side of housing 10 is then provided
accordingly with molding 26 and elastic body 32 for the respective
terminal fittings.
Regardless of whether the front side of the housing is provided
with rigid and/or elastic bodies, the end cap can also be connected
permanently to one or more terminal fittings and cables. Since, in
this case however, replacement, for example, of only one of the
cable sets would not be not possible, this embodiment is less
preferred.
FIG. 4 shows, in a section similar to that of FIG. 3, a further
modified embodiment of the implantable unit in which engagement
between the housing and sealing cap takes place via a catch
connection instead of via a screw connection. For this reason, end
cap 18 has one or more catch projections 37 on the inside of the
edge thereof which faces housing 10. Projections 37 fit into
housing recesses 38 when the housing and end cap are joined. In the
embodiment shown in FIG. 4, recess 38 is formed by a projecting
edge of the molding 26 which is attached to the side of the housing
that contains feedthroughs 22. It goes without saying that a
functionally analogous catch connection between the end cap and the
housing 10 can be achieved independent of the shape of molding 26
by a corresponding configuration of end cap 18 and housing 10
themselves.
In order to be able to vary contact force F.sub.K and sealing force
F.sub.D, also when using a catch connection, one or more further
recesses can be provided parallel to the recess 38 at varying
heights. Alternatively, the component which is engaged by the catch
projection 37 can have a sawtoothed surface allowing the height at
which projection 37 is held relative to the housing 10 to be
varied.
The following underlying functional parameters of the connection
principle are shown in FIGS. 5 and 6:
diameter of the gas-tight point of contact .O slashed..sub.K
Diameter .O slashed..sub.K must be selected to be so large that
current carrying capacity is ensured for the selected metallic
material.
diameter of the elastically supported contact .O slashed..sub.S
Diameter .O slashed..sub.S must be selected to be so large that the
elastic, electrically insulating material which is preferably made
of silicone is not damaged and is not stressed beyond its elastic
limit when the resilient restoration force is generated.
deformation path s
When the terminal fitting abuts the body located on the front side
of the housing, the sealing lands are pressed by the closure
mechanism into the molding by the length of deformation path s. The
resulting restoration force produces sealing force F.sub.D and
contact force F.sub.K. Shore hardness X and the elastic limit of
the elastic material play a role in this case.
Shore hardness X
The higher the Shore hardness of the elastic material, the higher
the reset force for a given deformation path.
Projecting height of the contact h.sub.K
The force produced with the closure mechanism generates both the
pressure on the sealing lands and also on the points of contact. If
the projecting height of the contact h.sub.K and the height of
sealing lands h.sub.D are selected to be the same, the pressure is
distributed proportionally to the respective surfaces and is
produced by the spring action of the elastic material under
deformation path s. If the projecting height of the contact h.sub.K
is selected to be different than the height of sealing land
h.sub.D, the entire deformation path s takes effect only for one of
the two contacts. In this way, the pressure to be produced on the
point of contact and the pressure to be produced on the sealing
lands can be adjusted independently of their surface ratios.
height of sealing lands h.sub.D
The aforementioned relation to the projecting height of the contact
applies. The required height of the sealing land depends on the
overall geometry of the sealing lands, the elastic material, and
its Shore hardness. If maximum pressure on the sealing lands is to
prevail, the elastic material should not be pressed against the
molding between the sealing lands. The height must be selected
accordingly and corresponds at most to deformation path s.
width of sealing lands b.sub.D
The narrower the sealing lands which are selected, the higher the
pressure, but the elastic material should not be damaged.
For a current carrying capacity in the mA range, the amount of
space required by the contact arrangements as compared to the
aforementioned standardized cardiac pacemaker plug-and-socket
connections can be significantly minimized.
The closing mechanism must press the terminal fittings against the
housing with a defined closing force, so that a gas-tight contact
closure is formed and the sealing effect is ensured. Before the
force acts on the elastic material which produces a spring-like
restoration force via deformation path s, the terminal fittings
must be in the exactly correct position. One simple solution is to
insert the terminal fittings into the end cap which is drawn
against the housing using a screw with defined torque. This process
is, however, only conditionally possible if the housing is already
anchored in the bone bed since sealing takes place from the
front.
To be able to operate the closing mechanism from overhead, in the
modified embodiment illustrated in FIGS. 7 and 8, housing 40 has a
type of trough 42 on its front end into which terminal fittings 44
are inserted from above. These terminal fittings are moved into the
exact position using cover 46, which is mounted in the area of
trough 42, and then are pressed against housing 40 by inserting a
wedge 48 for a defined deformation distance. The peripheral out
line of the terminal fittings 44 and the corresponding
accommodation in trough 42 can be made in the aforementioned manner
such that no terminal fitting fits into the receiver of another.
Furthermore, FIG. 7 shows terminal fitting 44 which is designed for
a four-pole connection.
According to FIG. 8, after inserting terminal fittings 44 into
trough 42, cover 46 is mounted. By means of opening 50 in the cover
46, wedge 48 is placed between terminal fittings 44 and the side of
wall 51 of trough 42 which is remote from housing 40, so that
terminal fittings 44 are pushed by the defined deformation distance
in the direction toward wall housing surface 54 having the
contacts, and are pressed against this surface. In this case, wedge
48 can be placed and fixed using a screw 52, or a catch mechanism
(not shown) can be provided by means of which manually inserted
wedge 48 is fixed in the installation position.
The above described connection principle between a device to be
implanted and actuator and/or sensor components allows an
insulation impedance between the individual contacts of more than
50 M.OMEGA., this value exceeding the insulation impedance of 50
k.OMEGA. required by the aforementioned DIN standard for cardiac
pacemakers by several-fold. For example, in an implantable hearing
aid, gains of >80 dB between the sensor and actuator are
necessary without feedback occurring between the sensor signals and
the actuator signals, and it should be possible to transmit analog
signals in the microvolt range without distortion via the contact
arrangement. The proposed implantable unit, thus, makes it possible
to satisfy the high demands which apply to contact-making for
implantable hearing aids and which correspond to the requirements
of signal transmission in the audio and HiFi range.
In spite of a high degree of possible miniaturization, closing of
the contact arrangements takes place easily, reliably and safely.
Without using the typical male and female design of contacts in the
form of a pin and receiving socket, there is no danger, in the
proposed system, that the contacts can be broken, bent or otherwise
damaged.
While various embodiments in accordance with the present invention
have been shown and described, it is understood that the invention
is not limited thereto, and is susceptible to numerous changes and
modifications as known to those skilled in the art. Therefore, this
invention is not limited to the details shown and described herein,
and includes all such changes and modifications as are encompassed
by the scope of the appended claims.
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